The present invention deals with an emboli capturing system. More specifically, the present invention deals with an emboli capturing system and method for capturing embolic material in a blood vessel during an atherectomy or thrombectomy procedure.
Blood vessels can become occluded (blocked) or stenotic (narrowed) in a number of ways. For instance, a stenosis may be formed by an atheroma, which is typically a harder, calcified substance which forms on the lumen walls of the blood vessel. A stenosis may also be formed of a thrombus material, which is typically much softer than an atheroma but can nonetheless cause restricted blood flow in the lumen of the blood vessel. Thrombus formation can be particularly problematic in a saphenous vein graft ("SVG").
Two different procedures have been developed to treat a stenotic lesion (stenosis) in vasculature. One is deformation of the stenosis to reduce the restriction within the lumen of the blood vessel. This type of deformation, or dilatation, is typically performed using balloon angioplasty.
Another method of treating stenotic vasculature is to attempt to completely remove the entire stenosis, or enough of the stenosis to relieve the restriction in the blood vessel. Removal of the stenotic lesion has been performed through use of radio frequency ("RF") signals transmitted via conductors, and also through use of lasers. Both of these treatments are intended to ablate (i.e., super heat and vaporize) the stenosis. Removal of the stenosis has also been accomplished using thrombectomy or atherectomy. During thrombectomy and atherectomy, the stenosis is mechanically cut or abraded away from the vessel. However, problems may be encountered during thrombectomy and atherectomy because the stenotic debris which is separated from the stenosis is free to flow within the lumen of the vessel. If the debris flows distally, it can occlude distal vasculature and cause significant problems. If it flows proximally, it can enter the circulatory system and form a clot in the neural vasculature or in the lungs, both of which are highly undesirable.
Prior attempts to deal with the debris or fragments produced during thrombectomy and atherectomy have included cutting the debris into pieces small enough (having a size on the order of a blood cell) that they will not occlude vessels within the vasculature. However, this technique has certain problems. For instance, it is difficult to control the size of the fragments which are severed from the stenotic lesion. Larger fragments may be severed accidentally. Also, since thrombus is much softer than an atheroma, it tends to break up easier when mechanically engaged by a cutting instrument. Therefore, at the moment that the thrombus is mechanically engaged, there is a danger that it can be dislodged in large fragments which would occlude the vasculature.
Another attempt to deal with debris severed from a stenosis is to remove the debris as it is severed, using suction. However, it may be necessary to pull quite a high vacuum in order to remove all of the pieces severed from the stenosis. If the vacuum used is not high enough, all of the severed pieces will not be removed. Further, use of a high vacuum may tend to cause the vasculature to collapse.
A final technique for dealing with the fragments severed during atherectomy of the stenosis is placement of a device distal to the stenosis during atherectomy to catch the pieces of the stenosis as they are severed, and removal of those pieces along with the capturing device when the atherectomy procedure is complete. Such capture devices have included expandable filters which are placed distal of the stenosis to capture stenosis fragments. Problems are also associated with this technique. For example, delivery of such devices in a low-profile pre-deployment configuration can be difficult. Further, some devices include complex and cumbersome actuation mechanisms. Also, retrieving such capture devices, after they have captured emboli may be difficult.